The window glass used in automobiles, houses, and the like transmits both the visible light and the infrared light emitted from the sun and the like, and hence the internal temperature of the automobiles or the houses rise. Accordingly, lots of energy needs to be used to control the internal temperature. Therefore, a heat ray-shielding film which transmits visible light but shields infrared light is bonded to the window glass so as to prevent the rise of the internal temperature.
As a heat-ray shielding material used in the heat ray-shielding film, a heat ray-shielding coating composition is used which is obtained by dispersing metal oxide particles reflecting⋅absorbing heat rays, such as tin oxide, antimony-doped tin oxide (ATO), and tin-doped indium oxide (indium tin oxide, ITO) or an organic compound shielding heat rays, such as a phthalocyanine compound, in a transparent resin such as an acrylic resin, a methacrylic resin, an epoxy resin, a urethane resin, a polyester resin, or a polystyrene resin (for example, Patent Literature No. 1).
The heat ray-shielding coating composition is prepared by mixing together a cross-linkable compound having a methacryloyl group or an acryloyl group as a reactive functional group, metal oxide particles or metal composite oxide particles such as antimony tin oxide (ATO), indium tin oxide (ITO), or vanadium oxide, a polymerization initiator, and a dispersant so as to obtain a coating composition. Therefore, in a case where the coating composition is cured, a polymerization reaction poorly occurs between the cross-linkable compound and the surface of the metal oxide particles or the metal composite oxide particles. Accordingly, the heat-ray shielding properties, transparency, and abrasion resistance of the obtained coating material deteriorate. Particularly, in a case where heat ray-shielding properties are imparted to the surface of front glass or window glass, unfortunately, transparency and abrasion resistance are not sufficiently obtained.
The physiological discomfort (hereinafter, referred to as “scorching sensation” in some cases) the skin feels as if it is scorched when being irradiated with light is greatly affected by infrared rays of a wavelength of 1,500 nm to 2,100 nm (for example, Non Patent Literature No. 1). Within the above wavelength region, sunlight (solar radiation light) has a certain intensity at a wavelength of 1,450 nm to 1,750 nm. Accordingly, particularly by shielding infrared rays of a wavelength of 1,450 nm to 1,750 nm, the scorching sensation can be suppressed. Therefore, there is a demand for a resin composition and a heat ray-shielding film exhibiting heat ray-shielding properties within the aforementioned wavelength region.